1. Field of the Invention
This invention relates to silicone foam containing water as one of the agents used to create the foam.
2. Background Information
Over the years, the use of elastomeric foams of various types have become the standard for cushioning materials, both for seats and for packaging and for gasketing. Various uses require a variety of properties of the foams depending upon how they are used. Some cushioning applications require a very soft, open-cell foam which is easily compressed while other applications require a firm, closed-cell foam which is density, flammability, and toxicity become important in some uses. Because of the wide variety of combinations required, many different methods of producing various types of foam have been developed.
A method of making an organosiloxane foam is described by Smith in U.S. Pat. No. 3,923,705, issued Dec. 2, 1975. His method mixes an organohydrogensiloxane, a hydroxylated organosiloxane, and a platinum catalyst, where the molar ratio of silicon-bonded hydrogen atoms to silicon-bonded hydroxyl radicals of 2.5 to 40 is specified. He also describes the use of polymethylvinylsiloxane cyclics to retard foaming and curing reactions, the addition of carbon black, and the use of vinyl-containing polydiorganosiloxane up to 85 weight percent of the combined weight of hydroxylated polydiorganosiloxane and vinyl-containing polydiorganosiloxane. In the later instance, the molar ratio of silicon-bonded hydrogen atoms to silicon-bonded hydroxyl radicals is 0.5 to 40.
A foam composition useful as insulation for electrical systems which does not burn easily is taught by Modic in U.S. Pat. No. 4,189,545, issued Feb. 19, 1980. The novel foaming agent is water. His foam composition comprises a base vinyl-containing polydiorganosiloxane, from 100 to 15,000 parts per million of water, a silicone hydride having a hydrogen content of from 0.3 to 1.6 percent by weight where there is at least 0.2 moles of SiH per mole of water, and platinum catalyst.
Another composition is taught by Modic in British Specification No. 2,065,661 A, published July 1, 1981. In this case, he points out that the composition containing water separates upon standing and must be remixed before it can be used. The composition of this British application therefore comprises a base vinyl-containing polymer, from 1 to 10 parts by weight of silanol-containing compound having a viscosity of from 10 to 1,000 centipoise at 25.degree. C., a silicone hydride where there is at least 1 mole of SiH per mole of silanol, and a platinum catalyst.
Compositions such as these produce silicone foam which has fire retardant properties, but there is still a need for silicone foam of improved compressibility and lower density while still retaining useful strength. Such foams still retain the superior weatherability, lower toxicity, and longer life of silicone based foam as compared to organic foams such as urethane based foam.